Apparatus and method for ionizing an analyte, and apparatus and method for analysing an ionized analyte

ABSTRACT

The present invention discloses an ionization apparatus  10  for ionizing an analyte S, comprising an inlet E, an outlet A, a first electrode  1 , a second electrode  2  and a dielectric element  3 . The first electrode  1 , the second electrode  2  and the dielectric element  3  are arranged relative to one another such that, by applying an electric voltage between the first electrode  1  and the second electrode  2 , a dielectric barrier discharge is establishable in a discharge area  5  in the ionization apparatus  10 . The first and second electrodes  1, 2  are arranged such that they are displaceable or movable relative to each other.

The present invention relates to the technical field of ionizing ananalyte, in particular the ionizing or ionization of a substance in acarrier gas in preparation for its analysis.

Various ionization apparatuses based on a dielectric barrier discharge,which are used in various processes for ionization, are known from theprior art. After the ionization of an analyte, the latter can beanalyzed.

US 2012 02 92 526 A1 discloses an ionization apparatus in which asampling nozzle, an ion supply tube leading to an analysis apparatus anda dielectric barrier discharge tube are connected to a T-shaped tube.

However, the apparatuses and methods known from the prior art often havea comparatively low sensitivity, they fragment the analyte (thus makingspectra established by subsequent analysis difficult to interpret) andthey require a high constructional outlay.

It is the object of the present invention to provide an apparatus bymeans of which a discharge gas and an analyte are ionizable in aflow-through process and which, mainly, does not fragment the analyte,or fragments it only to a minor extent, which can be used under ambientconditions so as to avoid a high constructional outlay and high costs ofequipment and which guarantees high sensitivity in a possible analysisof an ionized substance.

This object is achieved by an ionization apparatus according to claims1, 14, 26, 38, 81 and by a method according to claims 8, 19, 31, 48, 89as well as by an analyzer according to claims 54, 71 and by a methodaccording to claims 65, 76.

The present invention is able to accomplish a flow-through ionization ofan analyte, in particular for the purpose of analysis. In this respect,a so-called “soft” ionization can be applied, which, for the most part,does not destroy or fragment molecules, but leads to quasi-molecularions through protonation reactions and charge-transfer reactions.Especially in combination with (high-resolution) mass spectrometry, thesubstance can thus be identified directly via its elemental composition.Due to the way in which the ionization apparatuses and ionizationmethods according to the present invention as well as the analyzer andthe analysis method according to the present invention are configured, avery high sensitivity in the low femtogram to attogram range can beaccomplished in a subsequent analysis.

The invention provides highly efficient ionization apparatuses (and amethod associated therewith) as well as an analyzer (and a methodassociated therewith), which, in combination with mass spectrometry orion mobility spectrometry, provide a highly sensitive “electronic nose”(in an analysis method) allowing a direct chemical analysis of moleculesin the gaseous phase.

Application possibilities are, in addition to classical combinationswith chromatographic methods (GC, HPLC, Nano-LC), also direct screeninganalyses, e.g. a direct pesticide analysis on fruit or vegetablesurfaces.

For military or civil defense purposes, the technology may be used todetect toxic compounds or warfare agents. Especially in the case ofchemical warfare agents, a very high sensitivity is required, since eventhe smallest concentrations of these agents may lead to poisoning thatis dangerous to life.

Another related field of application is forensics or security checks(narcotic or explosive wipe tests).

Also a combination with sample preconcentration systems, such as SPME,is possible. The method can be used for medical “point of care”diagnostics (e.g. biomarker analysis in breath or in combination withSPME for hazardous and prohibited substances in blood, urine etc.).

The possibility of flow-through ionization simplifies sampling duringanalysis in general (“sucking in” analogously to the human nose), andthis is important for rapid analysis applications or screening analyses,e.g. in industrial process control.

Furthermore, the hitherto existing problem of an effective transfer ofcharged particles at atmospheric pressure into a vacuum (analysis) issolved. Due to the mutual repulsion of the charged particles, largeparts of the ions formed are lost without being used in currentlyemployed processes for atmospheric pressure ionization (e.g. ESI, HESI,APCI, DART, DESI, LTP). The formation of ions directly in or at theinlet guarantees an effective transfer of the charged particles foranalysis and thus a high sensitivity.

Chemical analyses usually have to be carried out not only qualitativelybut also quantitatively. Due to the problem of an “open” connectionbetween the ionization and the analyzer, as with existing methods, thequantification may easily be interfered with by external influences(drafts, diffusion of impurities, etc.). This entails the problem ofwrong or incorrect analysis results. Through a flow-through ionization,the connection between ionization and analyzer is closed and theabove-described problem arising with respect to quantification is solvedin this way.

Existing plasma-based ionization processes or ionizing processes atquasi atmospheric pressure do not allow the analyte to be introducedinto the discharge gas, since the analyte is destroyed in the discharge.This problem is solved by the formation of an extremely “soft” plasmawith little fragmentation or no fragmentation at all.

Just like the efficiency, the degree of fragmentation occurring dependspartly on the composition of the surrounding atmosphere (humidity,etc.). Thus, a suitable selection of additive compounds (dopants) or gascompositions will allow to reduce or increase the ionization efficiencyand/or fragmentation. The latter is particularly useful for portableapplications, since portable systems themselves are usually not able togenerate characteristic fragments that are used to identify thesubstances.

Furthermore, the invention allows a miniaturization of analyzers and canbe combined with portable systems, whereby the sensitivity of the latterwill be increased substantially. In addition, operation with batteriesor rechargeable batteries is possible. Normally, no operating materials(except electrical energy) are required and analyses can be carried outin less than 100 ms. Furthermore, due to the miniaturizability and thestructural design of the present invention, the invention can becombined with other, already existing ionization methods (e.g. ESI,APCI, etc.), thus allowing simultaneous detection of different analytes,such as the parallel ionization of very polar and non-polar substances.

A further development of the ionization apparatus comprises theintroduction of so-called “dopant” substances (e.g. in chemicalionization) upstream or downstream of the ionization apparatus, for thepurpose of increasing the selectivity or the sensitivity.

An ionization apparatus for ionizing an analyte comprises an inlet, anoutlet, a first electrode, a second electrode, a dielectric element anda charge carrier filter. The first electrode, the second electrode andthe dielectric element are here arranged such that, by applying anelectric voltage, a dielectric barrier discharge is establishablebetween the first electrode and the second electrode in a discharge areain the ionization apparatus. The analyte can flow into the ionizationapparatus via the inlet. The analyte can flow through the discharge areaand flow out of the ionization apparatus via the outlet. The chargecarrier filter is arranged upstream of the outlet of the ionizationapparatus. The charge carrier filter is configured such that ions orcharged particles are filtered or selected on the basis of their type ofcharge.

Through the systematic selection (filtering) of reactive species, adefined ionization, which is easier to interpret or calculate, can beachieved in this way. In addition, this ionization by means of selectedreactant ions allows a quantification of the analyte species on thebasis of specific reaction coefficients even without intrinsiccalibration. Moreover, undesired ionization side reactions with highlyreactive or oxidizing species can be avoided, which, in turn, leads toeasier interpretable and more meaningful measurement results in anoptional subsequent analysis.

The charge carrier filter is preferably arranged after (downstream of)the discharge area.

The charge carrier filter may be configured such that a magnetic fieldcan be generated. Due to the magnetic field, ions or charged particlescan be filtered or selected on the basis of their type of charge. Thecharge carrier filter may also be a grid, especially a grid with anelectric potential or a grid to which an electric potential is applied.Also the grid allows ions or charged particles to be filtered orselected on the basis of their type of charge.

The ionization apparatus may comprise a first section and a secondsection. The first section may here comprise the inlet as a first inlet,the first inlet allowing a flow of discharge gas therethrough. Thesecond section may comprise a second inlet allowing a flow of analytetherethrough. The first section may be connected to the second sectionsuch that a flow therethrough can take place. The discharge area may belocated in the first section of the ionization apparatus.

With such a structural design, the analyte does not flow directlythrough the discharge area, but the discharge gas flows through thedischarge area, where it is ionized and, when the ionized discharge gasis brought into contact with the non-ionized analyte within theionization apparatus, at least part of the charges of the ionizeddischarge gas will be transferred to the analyte, so that the latterwill be ionized. This leads to a particularly soft ionization for theanalyte, and only very little fragmentation of the analyte is to beexpected.

Between the first electrode and the second electrode of the ionizationapparatus, the distance may be less than 20 mm, preferably less than 10mm, particularly preferred less than 5 mm and most preferred less than 2mm.

In particular, the distance describes the smallest distance between thefirst electrode and the second electrode, i.e. the distance between apoint of the first electrode and a point of the second electrode withthe smallest length value.

The first electrode may be in contact with the outer surface of thedielectric element. In particular, the first electrode may be configuredas a layer at or on the outer surface of the dielectric element.

By applying the electrode as a layer, parasitic discharges of theelectrode can be avoided, which may also occur when the distance (e.g.gas inclusions) between the first electrode and the dielectric elementis (very) small. The first electrode may be applied as a layer through adrying or curing liquid or suspension, e.g. through a metal paint.Likewise the layer may be applied on the outer surface of the dielectricelement through transition from a vapor phase to a solid phase. This canbe accomplished e.g. by sputtering, CVD or PVD, or other coatingtechniques.

One of the ionization apparatuses can be operated by a method. Accordingto this method, the analyte is introduced into the ionization apparatus,the analyte is ionized in the ionization apparatus, in particular by adielectric barrier discharge in the discharge area, and the ionizedanalyte is discharged from the ionization apparatus via the outlet.

Via the inlet as a first inlet, a discharge gas can be introduced intothe ionization apparatus and ionized in the discharge area. Via an inletor the second inlet, the analyte can be introduced into the ionizationapparatus and the analyte can be brought into contact with the ionizeddischarge gas in the ionization apparatus, so that an ionization of theanalyte will be carried out in the ionization apparatus.

The pressure in the ionization apparatus may be higher than 40 kPa,preferably higher than 60 kPa and particularly preferred higher than 80kPa. Most preferred, the pressure in the ionization apparatus issubstantially the atmospheric pressure. The substantially atmosphericpressure may allow a variation relative to atmospheric pressure of 10%above the atmospheric pressure or 10% below the atmospheric pressure.

Between the first electrode and the second electrode, an electricvoltage may be applied, so as to generate a dielectric barrierdischarge. The voltage may be a voltage of not more than 20 kV,preferably not more than 10 kV, particularly preferred not more than 5kV and most preferred between 1 kV and 3 kV.

The dielectric barrier discharge may be caused by unipolar high-voltagepulses. The pulse duration may here be not more than 1 μs, preferablynot more than 500 ns, and most preferred between 100 ns and 350 ns.

The high-voltage pulses may have a frequency of not more than 100 GHz,preferably not more than 100 MHz, particularly preferred not more than500 kHz and most preferred between 1 kHz and 100 kHz.

The first and the second electrodes may be supplied with a sinusoidalvoltage. The sinusoidal voltage of one of the electrodes may here beshifted by half a period duration with respect to the other one of thetwo electrodes.

A further ionization apparatus for ionizing an analyte comprises aninlet, an outlet, a first electrode, a second electrode and a dielectricelement. The first electrode, the second electrode and the dielectricelement are here arranged such that a dielectric barrier discharge canbe established in a discharge area in the ionization apparatus by anelectric voltage applied between the first electrode and the secondelectrode. The dielectric element has an outer surface, the first andthe second electrode being arranged on the outer surface of thedielectric element.

This allows in particular a miniaturization of the ionization source,while optimizing at the same time the flow profile, and this will be ofadvantage for the subsequent analysis carried out e.g. with portabledevices. In addition, undesirable fragmentation reactions, which may becaused by the electric discharge during plasma formation, caneffectively be suppressed by separating the plasma gas flow from theanalyte gas flow.

The ionization apparatus may comprise a capillary with an inlet. Thecapillary may be arranged, at least sectionwise, inside the dielectricelement.

The inlet may allow a flow of analyte into the capillary and the inletof the ionization apparatus may allow a flow of discharge gastherethrough. In the ionization apparatus, the flows of the dischargegas and of the analyte may be unitable.

The distance between the first electrode and the second electrode may beless than 20 mm, preferably less than 10 mm, particularly preferred lessthan 5 mm and most preferred less than 2 mm.

In particular, the distance is the smallest distance between the firstelectrode and the second electrode, the smallest distance beingdetermined as the length between a point of the first electrode and apoint of the second electrode with the smallest value.

One of the first and second electrodes or both the first electrode andthe second electrode may be in contact with the outer surface of thedielectric element. Preferably, the first electrode and/or the secondelectrode is/are configured as a layer, the layer being applied througha drying or curing liquid or suspension or through transition from avapor phase to a solid phase. This has the above described advantagethat parasitic discharges will be avoided.

One of the ionization apparatuses can be operated by a method. Themethod comprises the introduction of an analyte into the ionizationapparatus, the ionizing of the analyte in the ionization apparatus,preferably by a dielectric barrier discharge in the discharge area, andthe discharge of the ionized analyte from the ionization apparatus viathe outlet.

A discharge gas can be introduced into the ionization apparatus via theinlet, the discharge gas can be ionized in the discharge area and theanalyte can be introduced via an inlet of a capillary or the inlet ofthe capillary. The analyte can be brought into contact with the ionizeddischarge gas in the ionization apparatus, whereby an ionization of theanalyte is carried out.

The pressure in the ionization apparatus may be higher than 40 kPa,preferably higher than 60 kPa and particularly preferred higher than 80kPa. Most preferred, the pressure in the ionization apparatus issubstantially the atmospheric pressure. The substantially atmosphericpressure may allow a variation relative to atmospheric pressure of 10%above the atmospheric pressure or 10% below the atmospheric pressure.

Between the first electrode and the second electrode, an electricvoltage may be applied, so as to generate a dielectric barrierdischarge. The voltage may be a voltage of not more than 20 kV,preferably not more than 10 kV, particularly preferred not more than 5kV and most preferred between 1 kV and 3 kV.

The dielectric barrier discharge may be caused by unipolar high-voltagepulses. The pulse duration may here be not more than 1 μs, particularlypreferred not more than 500 ns, and most preferred between 100 ns and350 ns.

The high-voltage pulses may have a frequency of not more than 100 GHz,preferably not more than 100 MHz, particularly preferred not more than500 kHz and most preferred between 1 kHz and 100 kHz.

The first and the second electrodes may be supplied with a sinusoidalvoltage. The sinusoidal voltage of one of the electrodes may here beshifted by half a period duration with respect to the other one of thetwo electrodes.

A further ionization apparatus for ionizing an analyte comprises aninlet, an outlet, a first electrode, a second electrode and a dielectricelement. The first electrode, the second electrode and the dielectricelement are here arranged such that a dielectric barrier discharge canbe established in a discharge area in the ionization apparatus by anelectric voltage applied between the first electrode and the secondelectrode. At least one of the first and second electrodes is not fullycircumferential or is circumferentially interrupted.

In particular, at least one of the first and second electrodes isarranged on an outer surface of the dielectric element, which preferablyallows a flow therethrough, and is not fully circumferential or iscircumferentially interrupted. Circumferentially may here be understoodas a circumferential direction in a cylindrical coordinate system. Theaxial direction of the cylindrical coordinate system may here beunderstood to be parallel to the axis of the dielectric element and/orparallel to the (intended) flow direction in the ionization apparatus.

In particular, at least one of the first and second electrodes is notfully circumferential or is circumferentially interrupted in a planeperpendicular to a flow direction through the ionization apparatus.

This means that, in the case of a complete circulation of thecircumference (circumferential direction in cylindrical coordinates) ofthe first and second electrodes, at least one interruption may beformed, in particular in the plane perpendicular to the flow direction.

The structural design according to the present invention leads to one ora plurality of strongly localized plasma discharges (discharge areas).This has the effect that not the entire analyte flow passes through theplasma discharge (discharge area), but also through areas in which noplasma discharge (no discharge area) takes place. The undesirablefragmentation of the analyte through direct interaction with thedischarge can here be reduced. In addition, the length of the dischargepath as extension of the discharge areas can be adapted to the requiredapplication (from localized discharge points up to a discharge pathhaving a length of several centimeters in the axial direction), wherebythe number and the density of the reactive species and thus thefragmentation as well as the sensitivity can be adapted to therespective analytical application and optimized.

The first electrode may be located on the outer surface of thedielectric element.

The first electrode may, at least sectionwise, be spiral or helical inshape. Preferably, the spiral or helical section comprises at least onecomplete (360 degrees) winding, preferably the section comprises atleast five complete windings.

The first electrode may comprise at least two subelectrodes, the atleast two subelectrodes being spaced apart circumferentially, inparticular in the plane perpendicular to the flow direction. Each of thesubelectrodes may be connected to a control device via a respectiveline.

Preferably, the first electrode comprises four subelectrodes.

The subelectrodes may be arranged in a uniform manner in thecircumferential direction, so that, in the circumferential direction,the subelectrodes are spaced apart by the same distance or theinterruption between two respective subelectrodes is identical.

The subelectrodes may be circular in shape or rod-shaped.

The second electrode may be arranged, at least sectionwise, in thedielectric element. Preferably, the first electrode may be arrangedoutside the dielectric element.

The first electrode, the second electrode and the dielectric element maybe arranged relative to one another such that, by applying an electricvoltage between the first electrode and the second electrode, adielectric barrier discharge is establishable in at least two dischargeareas in the ionization apparatus, the two discharge areas being spacedapart axially in the flow direction and/or circumferentially, inparticular in a plane perpendicular to the flow direction.

Between the first electrode and the second electrode of the ionizationapparatus, the distance may be less than 20 mm, preferably less than 10mm, particularly preferred less than 5 mm and most preferred less than 2mm.

In particular, the distance describes the smallest distance between thefirst electrode and the second electrode, i.e. the distance between apoint of the first electrode and a point of the second electrode withthe smallest length value.

The first electrode may be in contact with the outer surface of thedielectric element. In particular, the first electrode may be configuredas a layer at or on the outer surface of the dielectric element. Byapplying the electrode as a layer, parasitic discharges of the electrodecan be avoided, which may also occur when the distance (e.g. gasinclusions) between the first electrode and the dielectric element is(very) small. The first electrode may be applied as a layer through adrying or curing liquid or suspension, e.g. through a metal paint.Likewise the layer may be applied through transition from a vapor phaseto a solid phase on the outer surface of the dielectric element. Thiscan be accomplished e.g. by sputtering, CVD or PVD, or other coatingtechniques.

One of the ionization apparatuses may be operated by a method. Themethod comprises the steps of introducing an analyte into the ionizationapparatus, ionizing the analyte in the ionization apparatus, anddischarging the ionized analyte from the ionization apparatus via theoutlet. Preferably, the analyte is ionized through a dielectric barrierdischarge in the discharge area or the discharge areas.

The pressure in the ionization apparatus may be higher than 40 kPa,preferably higher than 60 kPa, particularly preferred higher than 80kPa. Most preferred, the pressure in the ionization apparatus issubstantially the atmospheric pressure. The substantially atmosphericpressure may allow a variation relative to atmospheric pressure of 10%above the atmospheric pressure or 10% below the atmospheric pressure.

Between the first electrode and the second electrode, an electricvoltage may be applied, so as to generate a dielectric barrierdischarge. The voltage may be a voltage of not more than 20 kV,preferably not more than 10 kV, particularly preferred not more than 5kV and most preferred between 1 kV and 3 kV.

The dielectric barrier discharge may be caused by unipolar high-voltagepulses. The pulse duration may here be not more than 1 μs, preferablynot more than 500 ns and most preferred between 100 ns and 350 ns.

The high-voltage pulses may have a frequency of not more than 100 GHz,preferably not more than 100 MHz, particularly preferred not more than500 kHz and most preferred between 1 kHz and 100 kHz.

The first and second electrodes may be supplied with a sinusoidalvoltage. The sinusoidal voltage of one of the electrodes may be shiftedby half a period duration with respect to the other one of the twoelectrodes.

A further ionization apparatus for ionizing an analyte comprises aninlet, an outlet, a first electrode, a second electrode and a dielectricelement. The first electrode, the second electrode and the dielectricelement are arranged relative to one another such that, by applying anelectric voltage between the first electrode and the second electrode, adielectric barrier discharge is establishable in a discharge area in theionization apparatus. The first and second electrodes are arranged suchthat they are displaceable relative to each other.

Due to the displaceability of the electrodes, the extension of theplasma (the extension of the discharge area) and thus the number ofreactive species and the reaction space, respectively, can be adapted tothe respective analysis, in particular to the respective analyte, thusallowing the ionization efficiency or fragmentation to be adjusted,whereby the ion source can be adapted to the respective subsequentoptional analysis task (e.g. high or low sensitivity).

The electrodes may be arranged to be displaceable relative to each otherin a controllable manner, in particular the electrodes may bedisplaceable relative to each other by a controllable electric motor.

The first electrode and the second electrode may, at least sectionwise,be spiral or helical in shape.

The second electrode may, at least sectionwise, be arranged in thedielectric element. Preferably, the first electrode is arranged outsidethe dielectric element.

The displaceability of the first and second electrodes relative to eachother is given preferably in the flow direction or in a directionopposite to the flow direction through the ionization apparatus.

At least one of the first and/or second electrodes may comprise at leastone winding.

Between the first electrode and the second electrode of the ionizationapparatus, the distance may be less than 20 mm, preferably less than 10mm, particularly preferred less than 5 mm and most preferred less than 2mm. In particular, the distance describes the smallest distance betweenthe first electrode and the second electrode, i.e. the distance betweena point of the first electrode and a point of the second electrode withthe smallest length value.

Preferably, the first electrode is arranged to be displaceable relativeto the dielectric element. The second electrode may be arranged to benon-displaceable relative to the dielectric element.

One of the ionization apparatuses may be operated by a method. Accordingto this method, the analyte is introduced into the ionization apparatus,the analyte is ionized in the ionization apparatus, preferably through adielectric barrier discharge in the discharge area, and the ionizedanalyte is discharged from the ionization apparatus via the outlet.

The pressure in the ionization apparatus may be higher than 40 kPa,preferably higher than 60 kPa and particularly preferred higher than 80kPa. Most preferred, the pressure in the ionization apparatus issubstantially the atmospheric pressure. The substantially atmosphericpressure may allow a variation relative to atmospheric pressure of 10%above the atmospheric pressure or 10% below the atmospheric pressure.

Between the first electrode and the second electrode, an electricvoltage may be applied, so as to generate a dielectric barrierdischarge. The voltage may be a voltage of not more than 20 kV,preferably not more than 10 kV, particularly preferred not more than 5kV and most preferred between 1 kV and 3 kV.

The dielectric barrier discharge may be caused by unipolar high-voltagepulses. The pulse duration may here be not more than 1 μs, particularlypreferred not more than 500 ns, and most preferred between 100 ns and350 ns.

The high-voltage pulses may have a frequency of not more than 100 GHz,preferably not more than 100 MHz, particularly preferred not more than500 kHz and most preferred between 1 kHz and 100 kHz.

The first and the second electrodes may be supplied with a sinusoidalvoltage. The sinusoidal voltage of one of the electrodes may here beshifted by half a period duration with respect to the other one of thetwo electrodes.

An analyzer for analyzing an ionized analyte comprises an ionizationapparatus and an analysis unit. The ionization apparatus comprises aninlet, an outlet, a first electrode, a second electrode and a dielectricelement. The first electrode, the second electrode and the dielectricelement are arranged relative to one another such that, by applying anelectric voltage between the first electrode and the second electrode, adielectric barrier discharge is establishable between the firstelectrode and the second electrode in a discharge area. The ionizationapparatus is connected to the analysis unit. The connection isconfigured such that an analyte ionized in the ionization apparatus or(various) ionized analytes can flow out of the outlet of the ionizationapparatus directly into the analysis unit. The outlet of the ionizationapparatus and the first electrode or the discharge area are spaced apartin the flow direction (x-direction). The distance is less than 50 mm orthe outlet of the ionization apparatus and the first electrode overlapin the flow direction (x-direction).

The connection between the ionization apparatus and the analysis unit ishere configured such that, after a (first) ionization has taken placethrough a so-called reactive impact, a further reaction, caused e.g. bycharge transfer reactions, of the analyte or the analytes with areactive species, which has been formed in the plasma, will not bepossible. Both the ionization and the consecutive reactions depend onthe collision frequency of the molecules. This collision frequency maybe influenced by temperature and pressure.

By means of the structural design according to the present invention,ionization with kinetic product control is accomplished. This means thatthe analysis of the ionized analyte(s) takes place so quickly that thethermodynamic equilibrium aimed at by nature is not achieved or thatoccurrence of the equilibrium, e.g. when the ionized analyte(s) is/areintroduced into a vacuum, will be slowed down. As a result, suppressioneffects and competitive reactions, which normally occur in the case ofatmospheric-pressure ionization methods, will be suppressed effectively.In this way, not only can more analytes be ionized than before, but theycan reliably be quantified even in complex mixtures.

The ionized analyte may enter a vacuum chamber of the analysis unit. Thepressure prevailing in this vacuum chamber may be lower than the ambientpressure, in particular lower than the pressure prevailing in theionization apparatus.

Between the ionization apparatus and the vacuum chamber of the analysisunit, a pressure gradient may prevail. Preferably, the pressure gradientis at least 20 kPa, particularly preferred at least 50 kPa.

The distance between the outlet of the ionization apparatus and thefirst electrode may be adjustable.

The outlet of the ionization apparatus may be configured to bedisplaceable relative to the first electrode.

A reduction in size of the cross-section of the ionization apparatus ora restrictor may be arranged upstream of the outlet of the ionizationapparatus in the flow direction (x-direction). Preferably, the firstelectrode is arranged on the reduced cross-section or the restrictor.

The first electrode may be arranged on an outer surface of thedielectric element or it may be in contact with the outer surface.

The second electrode may be arranged, at least sectionwise, in thedielectric element.

The distance between the first electrode and the second electrode of theionization apparatus may be less than 20 mm, preferably less than 10 mm,particularly preferred less than 5 mm and most preferred less than 2 mm.This distance is in particular the smallest distance between the firstelectrode and the second electrode, i.e. it is the distance having thesmallest length value between a point of the first electrode and a pointof the second electrode.

The distance between the outlet of the ionization apparatus and thefirst electrode may be less than 40 mm, preferably less than 30 mm,particularly preferred less than 20 mm, even more preferred less than 10mm, and most preferred less than 5 mm. This applies to the flowdirection (x-direction).

The analysis unit may be a mass spectrometer or an ion mobilityspectrometer.

The outlet of the ionization apparatus may have a smallercross-sectional area than the inlet of the ionization apparatus.

One of the analyzers may be used for a method for analyzing an analyte.The method comprises the steps of introducing an analyte into theionization apparatus, ionizing the analyte, preferably by a dielectricbarrier discharge in the discharge area, discharging the ionized analytefrom the ionization apparatus via the outlet into the analysis unit, andanalyzing the analyte in the analysis unit.

The pressure in the ionization apparatus may be higher than 40 kPa,preferably higher than 60 kPa, particularly preferred higher than 80kPa. Most preferred, the pressure in the ionization apparatus issubstantially the atmospheric pressure. The substantially atmosphericpressure may allow a variation relative to atmospheric pressure of 10%above the atmospheric pressure or 10% below the atmospheric pressure.

Between the first electrode and the second electrode, an electricvoltage may be applied, so as to generate a dielectric barrierdischarge. The voltage may be a voltage of not more than 20 kV,preferably not more than 10 kV, particularly preferred not more than 5kV and most preferred between 1 kV and 3 kV.

The dielectric barrier discharge may be caused by unipolar high-voltagepulses. The pulse duration may here be not more than 1 μs, particularlypreferred not more than 500 ns, and most preferred between 100 ns and350 ns.

The high-voltage pulses may have a frequency of not more than 100 GHz,preferably not more than 100 MHz, particularly preferred not more than500 kHz and most preferred between 1 kHz and 100 kHz.

The first and second electrodes may be supplied with a sinusoidalvoltage. The sinusoidal voltage of one of the electrodes may here beshifted by half a period duration with respect to the other one of thetwo electrodes.

A further analyzer for analyzing an ionized analyte may comprise anionization apparatus and an analysis unit. The ionization apparatuscomprises an inlet, an outlet, a first electrode, a second electrode anda dielectric element. The first electrode, the second electrode and thedielectric element are arranged relative to one another such that, byapplying an electric voltage between the first electrode and the secondelectrode, a dielectric barrier discharge is establishable in adischarge area. The ionization apparatus is connected to the analysisunit such that an analyte or (various) analytes ionized in theionization apparatus can flow out of the outlet of the ionizationapparatus directly into the analysis unit. The ionization apparatus isconfigured and connected to the analysis unit such that the analyte canflow over a distance between the discharge area and the analysis unit inless than 1 s.

The distance between the discharge (the discharge area) and the analysisunit may here be dimensioned such that the ionization time or dwelltime, which results from the flow-through volume at the beginning of theplasma discharge (discharge area) and the flow velocity, is less than 1s, preferably less than 500 ms, particularly preferred less than 200 ms,even more preferred less than 50 ms, and most preferred less than 20 ms,prior to the analysis or the suppression of ionization (e.g. byintroduction into a vacuum).

The flow-through volume comprises here the distance between thedischarge area or the beginning of the plasma discharge and the analysisor the suppression of ionization (e.g. by means of a vacuum) and thecross-section through which the flow takes place. The cross-sectionthrough which the flow takes place need not be constant throughout thedistance over which the flow takes place.

The distance of the bringing together of reactive species (e.g. in adischarge gas) and the analyte relative to the analysis unit may bedimensioned such that the ionization time (reaction time of the analytewith reactive species), which results from the flow-through volumebeginning at the first contact time of the analyte molecules with thereactive species formed by the plasma discharge and the flow velocity,is less than 1 s, preferably less than 500 ms, particularly preferredless than 200 ms, even more preferred less than 50 ms, and mostpreferred less than 20 ms, prior to the analysis or the suppression ofionization (e.g. by introduction into a vacuum).

The reactive species and analyte can be brought together directly in thedischarge or later on (downstream). An ionization of the analyte takesplace during the first local contact of the analyte with the reactivespecies.

These usually metastable plasma species are normally detected by optical(spectroscopic) methods, since they exhibit characteristic emissions orabsorption lines. This allows a discharge area or a discharge to belocalized.

By means of the structural design according to the present invention,ionization with kinetic product control is again accomplished, and thiswill entail the above described effects and advantages.

The analysis unit may comprise a vacuum chamber and the ionizationapparatus may be connected to the analysis unit such that the analytecan enter the vacuum chamber of the analysis unit directly. Inparticular, the ionization apparatus may be connected to the analysisunit such that the analyte can flow over the distance between thedischarge area and the vacuum chamber in less than 1 s.

A flow over the distance between the discharge area and the analysisunit or the vacuum chamber of the analysis unit can take place in lessthan 500 ms, preferably in less than 200 ms, particularly preferred inless than 50 ms, most preferred in less than 20 ms.

In the case of a volume flow through the ionization apparatus of lessthan 20 L/min, preferably less than 10 L/min, particularly preferredless than 5 L/min, most preferred less than 2.5 L/min, the analyte (S)can flow over the distance between the discharge area and the analysisunit or the vacuum chamber of the analysis unit within a time lyingbelow the respective upper time limit.

Between the ionization apparatus and the vacuum chamber of the analysisunit, a pressure gradient may prevail. Preferably, the pressure gradientis at least 20 kPa, particularly preferred at least 50 kPa.

The distance between the outlet of the ionization apparatus and thefirst electrode may be adjustable.

The outlet of the ionization apparatus may be configured to bedisplaceable relative to the first electrode.

A reduction in size of the cross-section of the ionization apparatus ora restrictor may be arranged upstream of the outlet of the ionizationapparatus in the flow direction (x-direction). Preferably, the firstelectrode is arranged on the reduced cross-section or the restrictor.

The first electrode may be arranged on an outer surface of thedielectric element or it may be in contact with the outer surface.

The second electrode may, at least sectionwise, be arranged in thedielectric element.

The distance between the first electrode and the second electrode of theionization apparatus may be less than 20 mm, preferably less than 10 mm,particularly preferred less than 5 mm and most preferred less than 2 mm.In particular, this distance is the smallest distance between the firstelectrode and the second electrode, i.e. it is the distance with thesmallest length value between a point of the first electrode and a pointof the second electrode.

The distance between the outlet of the ionization apparatus and thefirst electrode is less than 40 mm, preferably less than 30 mm,particularly preferred less than 20 mm, even more preferred less than 10mm, and most preferred less than 5 mm. This applies to the flowdirection (x-direction).

The analysis unit may be a mass spectrometer or an ion mobilityspectrometer.

The outlet of the ionization apparatus may have a smallercross-sectional area than the inlet of the ionization apparatus.

One of the analyzers may be used for a method for analyzing an analyte.The method comprises the steps of introducing an analyte into theionization apparatus, ionizing the analyte, preferably by a dielectricbarrier discharge in the discharge area, discharging the ionized analytefrom the ionization apparatus via the outlet into the analysis unit, andanalyzing the analyte in the analysis unit.

The pressure in the ionization apparatus may be higher than 40 kPa,preferably higher than 60 kPa, particularly preferred higher than 80kPa. Most preferred, the pressure in the ionization apparatus issubstantially the atmospheric pressure. The substantially atmosphericpressure may allow a variation relative to atmospheric pressure of 10%above the atmospheric pressure or 10% below the atmospheric pressure.

Between the first electrode and the second electrode, an electricvoltage may be applied, so as to generate a dielectric barrierdischarge. The voltage may be a voltage of not more than 20 kV,preferably not more than 10 kV, particularly preferred not more than 5kV and most preferred between 1 kV and 3 kV.

The dielectric barrier discharge may be caused by unipolar high-voltagepulses. The pulse duration may here be not more than 1 μs, particularlypreferred not more than 500 ns, and most preferred between 100 ns and350 ns.

The high-voltage pulses may have a frequency of not more than 100 GHz,preferably not more than 100 MHz, particularly preferred not more than500 kHz and most preferred between 1 kHz and 100 kHz.

The first and second electrodes may be supplied with a sinusoidalvoltage. The sinusoidal voltage of one of the electrodes may here beshifted by half a period duration with respect to the other one of thetwo electrodes.

A further ionization apparatus for ionizing an analyte comprises a firstinlet, a second inlet, an outlet, a first electrode, a second electrodeand a dielectric element. The first electrode, the second electrode andthe dielectric element are here arranged relative to one another suchthat, by applying an electric voltage between the first electrode andthe second electrode, a dielectric barrier discharge is establishablebetween the first electrode and the second electrode in a discharge areain the ionization apparatus. The first and second electrodes arearranged such that they are displaceable relative to each other.

By displacing the electrode, the plasma can be formed closer to or moreremote from a point of coming together with the analyte. This allowsdifferent reactive components of the plasma to react with the analyte,since the plasma components have life states of different lengths. Theionization efficiency and the fragmentation can thus be controlleddirectly, since shorter-lived species are generally more reactive thanlong-lived species.

The second electrode may comprise a section that curves outwards in ther-direction.

The first electrode and/or the dielectric element may comprise a sectionthat curves outwards in the r-direction. The section of the secondelectrode that curves outwards in the r-direction and the section of thefirst electrode and/or of the dielectric element that curves outwards inthe r-direction may be configured in a corresponding manner. Therespective curved section is here configured in a substantially uniformmanner.

The section of the second electrode that curves outwards in ther-direction may be displaceable in the section of the first electrodeand/or of the dielectric element that curves outwards in ther-direction.

The displaceability of the second electrode relative to the firstelectrode and/or the dielectric element may here be limited by thestructural design of the curved section of the first electrode and/orthe dielectric element.

The second electrode may, at least sectionwise, be arranged in thedielectric element. Preferably, the first electrode is arranged outsidethe dielectric element.

The displaceability of the first and second electrodes relative to eachother may be given in the flow direction or in a direction opposite tothe flow direction.

Between the first electrode and the second electrode of the ionizationapparatus, the distance may be less than 20 mm, preferably less than 10mm, particularly preferred less than 5 mm and most preferred less than 2mm. Preferably, the distance describes the smallest distance between thefirst electrode and the second electrode, the distance between a pointof the first electrode and a point of the second electrode exhibitingthe smallest length value.

The first electrode may be arranged to be non-displaceable relative tothe dielectric element. Preferably, the second electrode is arranged tobe displaceable relative to the dielectric element.

One of the ionization apparatuses can be operated by a method. Themethod comprises introducing an analyte into the ionization apparatus,ionizing the analyte in the ionization apparatus, in particular by meansof a dielectric barrier discharge in the discharge area, and dischargingthe ionized analyte from the ionization apparatus via the outlet.

The pressure in the ionization apparatus may be higher than 40 kPa,preferably higher than 60 kPa, particularly preferred higher than 80kPa. Most preferred the pressure in the ionization apparatus issubstantially the atmospheric pressure. The substantially atmosphericpressure may allow a variation relative to atmospheric pressure of 10%above the atmospheric pressure or 10% below the atmospheric pressure.

Between the first electrode and the second electrode, an electricvoltage may be applied, so as to generate a dielectric barrierdischarge. The voltage may be a voltage of not more than 20 kV,preferably not more than 10 kV, particularly preferred not more than 5kV and most preferred between 1 kV and 3 kV.

The dielectric barrier discharge may be caused by unipolar high-voltagepulses. The pulse duration may here be not more than 1 μs, preferablynot more than 500 ns, and most preferred between 100 ns and 350 ns.

The high-voltage pulses may have a frequency of not more than 100 GHz,preferably not more than 100 MHz, particularly preferred not more than500 kHz and most preferred between 1 kHz and 100 kHz.

The first and the second electrodes may be supplied with a sinusoidalvoltage. The sinusoidal voltage of one of the electrodes may here beshifted by half a period duration with respect to the other one of thetwo electrodes.

In general, the first and/or second electrode of the various embodimentsof the ionization apparatuses disclosed may consist of a materialconductive to electric current, such as metal. In particular, the firstand/or second electrode may comprise gold, silver or a metallic alloy(also in the form of a layer).

The first and/or second electrode of the various embodiments of thedisclosed ionization apparatuses may be configured as a hollow body(allowing a flow therethrough), e.g. as a ring or as a hollow cylinder,optionally with an interruption in the circumferential direction.

In the various embodiments of the disclosed ionization apparatuses, thefirst electrode may be arranged, at least sectionwise, outside thedielectric element and the second electrode may be arranged, at leastsectionwise, within the dielectric element.

In the various embodiments of the disclosed ionization apparatuses, thesecond electrode may be configured as a wire, which is arrangedconcentrically or eccentrically, at least sectionwise, in the dielectricelement.

The dielectric element of the various embodiments of the disclosedionization apparatuses may consist of a solid material and may inparticular consist of, or comprise, a plastic material (e.g. PMMA orPP). In particular, the dielectric element consists of quartz glass orcomprises quartz glass. Also various ceramics or ceramic compositematerials, such as corundum, are suitable materials.

In the various embodiments of the disclosed ionization apparatuses, theinlet of the ionization apparatus may be open to the surroundings, andthe discharge gas is the atmosphere, in particular air, surrounding theinlet. Also other discharge gases may be used, the discharge gas may,for example, contain nitrogen, oxygen, methane, carbon dioxide, carbonmonoxide or at least one noble gas, or mixtures thereof. In thedischarge area, a dopant may be present in addition to the dischargegas. Like the discharge gas, the dopant, e.g. methane, ethane, hydrogen,chlorobenzene or mixtures thereof or mixtures of various components, maybe introduced via the inlet of the ionization apparatus or via a furtherinlet into the ionization apparatus.

The dielectric barrier discharge within the various embodiments of theionization apparatus may also be established by applying a square-waveor sawtooth voltage or by other forms of alternating voltages known perse and having frequencies of 100 GHz or less.

The dielectric barrier discharge within the various embodiments of theionization apparatus may also be established by applying a directvoltage.

Generally, the various embodiments of the disclosed ionizationapparatuses may comprise an ion mass filter. Through an ion mass filter,a specific ion or specific ions are isolated or selected on the basis oftheir mass or their mass-to-charge ratio. An example of an ion massfilter is a quadrupole. An ion mass filter may be arranged between thedischarge area of an ionization apparatus and the inlet of theionization apparatus.

By arranging an analysis unit on one of the various embodiments of thedisclosed ionization apparatuses, an analyzer can be formed. Preferably,the ionization apparatus is directly connected to the analysis unit (ifnecessary, via a short intermediate element). The analysis unit arrangedis preferably a unit, which is able to execute an analysis on the basisof a molecular charge, e.g. a mass spectrometer, an ion mobilityspectrometer or comparable devices.

Preferably, an analyzer may have arranged therein, in addition to anionization apparatus, at least one further ionizing apparatus, e.g. anapparatus for executing electron impact ionization or electrosprayionization.

One of the disclosed ionization apparatuses may, in combination with ananalysis unit as an analyzer, be configured as a handheld device(portable device).

One of the disclosed ionization apparatuses may be used for flow-throughionization.

The embodiments of the present invention are described on the basis ofexamples and are not shown in a manner in which limitations from thefigures are transferred to or read into the claims.

FIG. 1 shows schematically an embodiment of an ionization apparatus 10with a first section 10 a and a second section 10 b.

FIG. 1a shows schematically an embodiment of an ionization apparatus 10with a first section 10 a, a second section 10 b and a grid 20 as acharge carrier filter.

FIG. 1b shows schematically an embodiment of an ionization apparatus 10with a first section 10 a, a second section 10 b and a magnet 21 as acharge carrier filter.

FIG. 2 shows schematically an embodiment of an ionization apparatus 10with first and second electrodes 1, 2 on an outer surface 3 a of adielectric element 3.

FIG. 3 shows schematically an embodiment of an ionization apparatus 10with subelectrodes 1 a, 1 b, . . . of the first electrode 1.

FIG. 3a shows schematically a section through the ionization apparatus10 of FIG. 3.

FIG. 3b shows schematically an embodiment of an ionization apparatus 10with a spirally-shaped or helically-shaped first electrode 1.

FIG. 3c shows schematically an embodiment of an ionization apparatus 10with subelectrodes 1 a, 1 b, . . . of the first electrode 1 and asectional view of this embodiment.

FIG. 4 shows schematically an embodiment of an ionization apparatus 10with first and second electrodes 1, 2 at a first position, theelectrodes being displaceable relative to each other.

FIG. 4a shows schematically an embodiment of an ionization apparatus 10with first and second electrodes 1, 2 at a second position, theelectrodes being displaceable relative to each other.

FIG. 5 shows schematically an embodiment of an analyzer 100 with anadjustable distance D2 between a first electrode 1 and an outlet A ofthe ionization apparatus 10.

FIG. 5a shows schematically an embodiment of an analyzer 100 with a moredetailed representation of the distance D2 between a first electrode 1and an outlet A of the ionization apparatus 10.

FIG. 6 shows schematically an embodiment of an ionization apparatus 10with an outwardly curved section 1 a of the first electrode 1.

FIG. 1 shows an ionization apparatus 10 comprising a first section 10 aand a second section 10 b.

The first section 10 a comprises an inlet E into which a discharge gas Gcan or will be introduced. The first section 10 a further comprises afirst electrode 1, a second electrode 2 and a dielectric element 3. Thedielectric element 3 is arranged between the first electrode and thesecond electrode 2. The first electrode 1 is arranged on an outersurface 3 a of the dielectric element 3. A dielectric barrier dischargecan be generated between the first electrode 1 and the second electrode2 by applying an electric voltage, the discharge taking primarily placein a discharge area 5.

When the discharge gas G flows via the inlet E into the first section 10a of the ionization apparatus 10, the discharge gas G will flow throughthe discharge area 5 and can be ionized in this area.

The first electrode 1 and the second electrode 2 are spaced apart by adistance D. The distance D is shown in FIG. 1 as the shortest distancebetween the first and second electrodes 1, 2.

The first section 10 a is connected to the second section 10 b in amanner allowing a flow therethrough or fluid communication, so that the(ionized) discharge gas G can flow from the first section 10 a into thesecond section 10 b. The second section 10 b comprises an inlet E2through which a sample or a sample substance or an analyte S can flowinto the second section 10 b.

In the area of the second section 10 b of the ionization apparatus,where the ionized discharge gas G flowing out of the first section 10 aand the analyte S are brought into contact, at least a part of thecharges of the ionized discharge gas G is transferred to the analyte S,the analyte S being thus ionized.

Via an outlet A in the second section 10 b of the ionization apparatus10, the ionized analyte S and the (ionized) discharge gas G leave theionization apparatus 10. Subsequently, the ionized analyte S can beanalyzed.

In the area of the outlet A in the second section 10 b of the ionizationapparatus 10, the cross-section is reduced in size so that thecross-sectional area of the outlet is smaller than the cross-sectionalarea of the inlet E2. The differences in cross-section serve the purposeof pressure control, among other things, since the flow through theionization apparatus 10 is typically caused by a pressure gradient. Thepressure outside the outlet A is here lower than the pressure outsidethe inlets E, E2 and in the ionizing apparatus 10. This vacuum can beaccomplished by a vacuum unit, e.g. a pump, connected to the outlet A(not shown in FIG. 1).

The inlet E2, into which an analyte S can be introduced, is typicallyopen to the surroundings.

Similar to the embodiment of an ionization apparatus 10 shown in FIG. 1,the ionization apparatus 10 of FIG. 1a comprises a first section 10 aand a second section 10 b, the sections 10 a, 10 b being in fluidcommunication.

In addition to the features and the mode of operation of the ionizationapparatus 10 shown in FIG. 1, a grid 20 is arranged in the first section10 a of the ionization apparatus 10 as a charge carrier filter after(downstream of) the discharge area 5. The grid 20 is connected to avoltage source (not shown in FIG. 1a ). Depending on the wiring of thegrid 20, positively charged particles or negatively charged particlescan pass through the grid 20, so that particles with the type of charge(positively or negatively charged) that cannot pass through the grid 20will be filtered. Examples of charged particles are ions and electrons.

The ionization apparatus 10 shown in FIG. 1b is similar to theionization apparatus 10 in FIG. 1a , the charge carrier filter providedbeing a magnet 21 instead of a grid 20 as in FIG. 1a . The magnet 21 isarranged after (downstream of) the discharge area 5 in the first section10 a of the ionization apparatus 10. The magnet 21 generates a magneticfield and allows charged particles of one type of charge (positive ornegative) to pass.

A further embodiment of an ionization apparatus 10 is shown in FIG. 2.The ionization apparatus 10 comprises a dielectric element 3 configuredin the form of a hollow cylinder. The dielectric element has an outersurface 3 a. The outer surface 3 a has arranged thereon a first and asecond electrode 1, 2, which are hollow cylindrical in shape. Thedielectric element 3 has arranged therein a capillary 30. The capillary30 is concentric with the dielectric element 3 and is hollow cylindricalin shape. Between the first and second electrodes 1, 2 a dielectricbarrier discharge can be caused in a discharge area 5. The dischargearea is primarily located in a space between the capillary 30 and thedielectric element 3.

Through the arrangement of the capillary 30 and of the dielectricelement 3, an inlet EK into the capillary and an inlet E into thedielectric element 3 are formed. Via the inlet E a discharge gas G canbe introduced into the ionization apparatus 10 and via the inlet EK ananalyte S can be introduced into the ionization apparatus 10. Thedischarge gas G can flow through the discharge area 5 and thus beionized.

The longitudinal dimension of the capillary 30 in a positive x-directionis shorter than the longitudinal dimension of the dielectric element 3in a positive x-direction, so that after (downstream) the analyte S hasflown through an outlet AK of the capillary 30, the flows of the ionizeddischarge gas G and the analyte S will be united and the ionizeddischarge gas G will be able to transfer at least part of its charge tothe analyte S, so that the analyte S will be ionized. The ionizedanalyte S can flow out of the ionization apparatus 10 through the outletA.

The flow in the ionization apparatus 10 may be caused by a vacuum unitat the outlet A (not shown in FIG. 2). The inlet EK to the capillary 30is preferably open to the surroundings.

The first electrode 1 and the second electrode 2 are spaced apart by adistance D, which, with a constant cross-section of the dielectricelement 3, results from the distance in an x-direction.

An embodiment of an ionization apparatus 10 comprising a not fullycircumferential or a circumferentially interrupted electrode 1 is shownin FIGS. 3 and 3 a.

The ionization apparatus 10 comprises a first electrode 1 consisting ofa plurality of subelectrodes 1 a, 1 b, . . . 1 h, a second electrode 2and a dielectric element 3 with an outer surface 3 a. In thecircumferential direction (cf. FIG. 3a ), a corresponding number ofinterruptions 1′ is formed between the respective subelectrodes 1 a, 1b, . . . 1 h. The subelectrodes 1 a, 1 b, . . . 1 h may be connected incommon to a control unit or a control device. A discharge gas G and ananalyte S can be introduced into the ionization apparatus via an inlet Eand discharged from the ionization apparatus 10 via an outlet A.

The second electrode 2 is here configured in the form of a wire, whilein other embodiments the second electrode may also be configured as ahollow body (allowing a flow therethrough), in particular as a hollowcylinder.

Between the second electrode 2 and the subelectrodes 1 a, 1 b, . . . 1 hof the first electrode 1, a dielectric barrier discharge isestablishable in a plurality of discharge areas 5 a, 5 b, . . . 5 h byapplying a voltage, the discharge areas 5 a, 5 b, . . . 5 h beingcircumferentially interrupted by the ionization apparatus 10 in a planeperpendicular to a flow direction R. The person skilled in the art willbe aware that a clearly defined delimitation of discharge areas in abinary sense will not always be fully possible, but that primarydischarge areas, where most of the discharge takes place, can beassigned.

In the embodiment according to FIGS. 3 and 3 a, the subelectrodes 1 a, 1b, . . . 1 h are circular in shape, while in other embodiments thesubelectrodes may also be configured as rectangles, in particular assquares.

A distance D between the first and second electrodes 1, 2 is given inFIG. 3 in the r-direction.

The embodiment of an ionization apparatus 10 in FIG. 3c is similar tothe embodiment according to FIGS. 3 and 3 a.

This ionization apparatus 10 comprises a second electrode 2, adielectric element 3 and a first electrode consisting of a plurality ofsubelectrodes 1 a, 1 b, . . . 1 h, the subelectrodes 1 a, 1 b, . . . 1 hbeing in contact with an outer surface 3 a of the dielectric element 3.

A discharge gas G and an analyte S can flow into an inlet E of theionization apparatus 10 and flow out of the ionization apparatus 10 viaan outlet A. The first electrode 1 (subelectrodes 1 a, 1 b, . . . 1 h)is a circumferentially interrupted or not fully circumferentialelectrode, since a plurality of interruptions or spaces 1′ is formedbetween the subelectrodes 1 a, 1 b, . . . 1 h. Between the subelectrodes1 a, 1 b, . . . 1 h and the second electrode 2, a dielectric barrierdischarge is establishable in a plurality of discharge areas 5 a, 5 b, .. . 5 h by applying a voltage. As regards the delimitation of dischargeareas, the above statements made in connection with the embodimentaccording to FIGS. 3 and 3 a apply. The subelectrodes 1 a, 1 b, . . . 1h may be connected in common to a control unit or a control device.

The second electrode 2 is configured in the form of a wire and is partlylocated inside the dielectric element 3.

In this embodiment, the subelectrodes 1 a, 1 b, . . . 1 h arerod-shaped, the subelectrodes 1 a, 1 b, . . . 1 h having a length (sidelength of the long sides) that is at least five times greater than theirwidth (end faces).

Due to the rod-shaped design of the subelectrodes 1 a, 1 b, . . . 1 h,the discharge areas 5 a, 5 b, . . . 5 h can be formed over a greateraxial length than in cases where shorter subelectrodes 1 a, 1 b, . . . 1h are used. Preferably, the length of the subelectrodes is at least 5 mmin an axial direction (x-direction). The distance D between the firstelectrode 1 (subelectrodes 1 a, 1 b, . . . 1 h) and the second electrode2 is constant over the axial length (x-direction) in the overlappingarea of the electrodes 1, 2.

In the embodiments according to FIGS. 3, 3 a and 3 c, the subelectrodes1 a, 1 b, . . . 1 h of the ionization apparatuses 10 are located atidentical axial (x-direction) distances from the inlet E and the outletA, i.e. they are arranged at identical axial positions, while in otherembodiments of ionization apparatuses 10, subelectrodes may also bearranged in an axially offset manner (not at identical axial positions).

In a further embodiment of an ionization apparatus 10, shown in FIG. 3b, the ionization apparatus 10 comprises a first electrode 1, a secondelectrode 2 and a dielectric element 3.

Via an inlet E, a discharge gas G and an analyte S can be introducedinto the ionization apparatus 10 and via an outlet A it can bedischarged therefrom. The discharge gas G and the analyte S can flowthrough the ionization apparatus in a flow direction R.

The first electrode 1 is contact with an outer surface 3 a of thedielectric element 3 and is spiral or helical in shape. In thisembodiment a plurality of windings is shown, while in other embodimentsalso at least one winding may be arranged. Preferably, at least twowindings, in particular at least five windings are provided.

Due to the helical or spiral design of the first electrode 1, the firstelectrode 1 is not fully circumferential or is circumferentiallyinterrupted in a plane perpendicular to the flow direction R. In thisplane a space or an interruption exists circumferentially betweenrespective sections of the first electrode 1. For a betterunderstanding, the first electrode is not shown in a sectional view inFIG. 3b , but, in a sectional view, the first electrode 1 would only bevisible in the form of axially offset points outside the dielectricelement 3.

Due to the helical or spiral design of the first electrode 1, the firstelectrode 1 is interrupted parallel to the flow direction R along adistance outside the dielectric element 3, or spaces (depending on thenumber of windings) are formed.

The second electrode 2 is configured in the form of a wire. The secondelectrode 2 is partly or sectionwise located inside the dielectricelement 3.

Between the first electrode 1 and the second electrode 2 a dielectricbarrier discharge is establishable in a discharge area 5 by applying avoltage. Due to the spiral or helical design, the discharge area 5 maybe interrupted parallel to the flow direction R along a distance insidethe dielectric element 3. Due to the spiral or helical design, thedischarge area 5 may be interrupted in a plane perpendicular to the flowdirection R, or it may not extend fully over an area in the plane,delimited by the dielectric element 3.

In a further embodiment of an ionization apparatus 10 according to FIGS.4 and 4 a, the ionization apparatus 10 comprises a first electrode 1, asecond electrode 2 and a dielectric element 3. A capillary 30, which isarranged sectionwise in the dielectric element 3, is connected to thesecond electrode 2 and the second electrode 2 is located inside thedielectric element 3.

The capillary 30 comprises an inlet E into which a discharge gas G andan analyte S can be introduced into the ionization apparatus 10. Anoutlet A of the ionization apparatus 10 can be used for discharging thedischarge gas G and the analyte.

The capillary 30 may also be replaced by some other element withdielectric properties.

The second electrode 2 is spiral or helical in shape. Similar to theillustration in FIG. 3b , the second electrode 2 is not shown in asectional view for better understanding. If FIGS. 4 and 4 a were asectional view, the second electrode 2 would be visible as axiallyoffset points.

A dielectric barrier discharge is establishable between the firstelectrode 1 and the second electrode 2, when a voltage is appliedbetween the electrodes 1, 2.

The first electrode 1 contacts an outer side 3 a of the dielectricelement 3 in such a way that the first electrode 1 can be displacedrelative to the dielectric element 3. The second electrode 2 cannot bedisplaced relative to the dielectric element 3, so that the firstelectrode 1 is displaceable relative to the second electrode 2.

Different positions of the first electrode 1 can be seen from FIGS. 4and 4 a. A look at the position of the first electrode 1 in FIG. 4 showsthat the first electrode 1 in FIG. 4a is displaced in a directionopposite to the flow direction R (in a negative x-direction). Thesedifferent positions of the first electrode 1 lead to overlapping areasof the first and second electrodes 1, 2 that overlap each other todifferent degrees in the flow direction R (x-direction).

For the position of the first electrode 1 according to FIG. 4, theoverlapping area of the first and second electrodes 1, 2 in the flowdirection R (x-direction) is larger than for the position of the firstelectrode 1 according to FIG. 4 a.

This results in an adaptability of the volume of the discharge area 5,through which the analyte S to be ionized flows, so that an adaptabilityof the ionization conditions to the analyte S is given and thesensitivity of a future analysis can be enhanced.

The distance D between the first and second electrodes 1, 2 is identicalat both positions (FIGS. 4 and 4 a) of the first electrode 1.

FIG. 5 shows schematically an analyzer 100 comprising an ionizationapparatus 10 and an analysis unit 40. Any disclosed ionization apparatus10 can be used in this analyzer, in addition to the ionization apparatus10 described representatively for this embodiment.

The ionization apparatus 10 comprises a first electrode 1, a secondelectrode 2 and a dielectric element 3.

The first electrode 1 is arranged outside the dielectric element 3 andthe second electrode 2 is located sectionwise inside the dielectricelement 3.

The second electrode 2 comprises an inlet E, through which a dischargegas G and an analyte S can be introduced into the ionization apparatus10.

Between the first and second electrodes 1, 2 a dielectric barrierdischarge is establishable in a discharge area 5 by applying a voltage.The first and second electrodes 1, 2 are spaced apart by a distance D.The discharge gas G and the analyte S can flow through the dischargearea 5, whereby at least the analyte S is ionized. An outlet of theionization apparatus 10 has connected thereto an analysis unit 40, e.g.a mass spectrometer or an ion mobility spectrometer. The ionized analyteS is analyzed (qualitatively and/or quantitatively) in the analyzer.

The end of the first electrode 1 (in a positive x-direction) with thedischarge area 5, in which or downstream of which the analyte S isionized, and the analysis unit 40 are spaced apart by a distance D2,preferably parallel to the flow direction R. The distance D2 isadjustable, in particular the positions of the first electrode 1 and ofthe second electrode 2 relative to each other remaining the same, whenthe distance D2 is changed.

The adjustability or variability of the distance D2 can be configured ina manner known per se.

Depending on the spatial dimensions of the ionization apparatus 10 andthe volume flow flowing through the latter, a time is obtained, in whichthe ionized analyte S flows with the (ionized) discharge gas G over thedistance D2 up to the point of analysis. Within this time, chemicaland/or physical processes can take place, which may change theionization state of the analyte S. For different analytes S, the optimumdistance D2 may be different, so that the latter can be adjusted fordifferent analytes S in an advantageous manner.

FIG. 5a shows an analyzer 100 according to a further embodiment. Theanalyzer 100 comprises an ionization apparatus 10 and an analysis unit40 with a vacuum chamber 41.

Any disclosed ionization apparatus 10 may be used as an ionizationapparatus 10, in addition to the ionization apparatus describedrepresentatively for this embodiment.

The ionization apparatus 10 comprises a first electrode 1, a secondelectrode 2 and a dielectric element 3 with an outer surface 3 a. Theionization apparatus 10 comprises an inlet E, through which a dischargegas G and an analyte S can be introduced into the ionization apparatus10, and an outlet A directly connected to the vacuum chamber 41 of theanalysis unit 40.

According to other embodiments, a transition piece or a transition linemay be arranged therebetween.

Between the first and second electrodes 1, 2, a dielectric barrierdischarge is establishable in a discharge area 5 by applying a voltagebetween the first and second electrodes 1, 2.

The first electrode 1 and the second electrode 2 are spaced apart by adistance D.

The pressure in the ionization apparatus 10 is higher than the pressurein the vacuum chamber 41, so that a pressure gradient Δp occurs betweenthe ionization apparatus and the vacuum chamber 41. Due to the pressuregradient Δp, the discharge gas G and the analyte S flow into the vacuumchamber 41 of the analysis unit 40, in which the ionized analyte S canbe analyzed (qualitatively and/or quantitatively).

The cross-section of the ionization unit 10 (allowing a flowtherethrough) tapers towards the outlet A of the ionization apparatus 10in the flow direction R, so that the inlet E has a largercross-sectional area than the outlet A. In other embodiments, thereduction in size of the cross-section of the outlet A may also berealized by a restrictor.

The first electrode 1 is arranged in the area of the taper, inparticular on the outer surface 3 a of the dielectric element 3 in thearea of the taper. The first electrode 1 and the outlet A are spacedapart by a distance D2 in the flow direction R or x-direction, while inother embodiments the distance D2 between the second electrode 2 and theoutlet A of the ionization apparatus may have to be taken into account,if the second electrode is located closer to the outlet A in the flowdirection R or x-direction. The first electrode 1 may also overlap theoutlet A in the flow direction R or x-direction, or the second electrode2 may overlap the outlet A of the ionization apparatus in the flowdirection R or x-direction, if the second electrode 2 is located closerto the outlet A of the ionization apparatus than the first electrode 1.

In particular, the distance D2 is less than 50 mm.

This has the effect that, in the case of a dielectric barrier discharge,the discharge area 5 will be located close to the outlet A and partly inthe outlet A in the flow direction R or x-direction.

A further embodiment of an ionization apparatus 10 is shown in FIG. 6.The ionization apparatus 10 comprises a first electrode 1, a secondelectrode 2 and a dielectric element 3 with an outer surface 3 a.

Between the first and second electrodes 1, 2 a dielectric barrierdischarge is establishable in various discharge areas 5 by applying avoltage.

The first electrode 1 is in contact with the outer surface 3 a of thedielectric element 3 and has a section 1 a that curves outwards in ther-direction and corresponds to or is identical in shape with a section 3a of the dielectric element that curves outwards in the r-direction.

The dielectric member 3 has an inlet E3 through which a discharge gas Gcan flow into the ionization apparatus.

The second electrode 2 has an inlet E, through which an analyte S can beintroduced into the ionization apparatus 10, and a section thereof islocated inside the dielectric element 3. The second electrode 2 has anoutwardly curved section 2 a or a section of increased thicknesspartially arranged in the curved section 3 a of the dielectric element.

The first electrode 1 and the second electrode 2 are spaced apart by adistance D.

The second electrode 2 is displaceable relative to the first electrode 1and the dielectric element 3, in particular in the flow direction R orx-direction. A displacement of the second electrode 2 relative to thefirst electrode 1 results in different positions of the discharge area5, FIG. 6 showing one of the possible positions.

When a discharge gas G flows into the inlet E3 of the dielectric element3 and through the discharge area 5, the ionized discharge gas G has tocover a longer distance until the ionized discharge gas comes intocontact with the analyte, which has flown into the inlet E of the secondelectrode 2, and transfers at least part of its charges to the analyte Sso as to ionize the analyte. Due to the possibility of changing thelength of the distance (corresponding to a change in the length of timeunder otherwise identical conditions) over which the ionized dischargegas G has to flow until it comes into contact with the analyte S to beionized, an improved adaptability of the ionization apparatus 10 todifferent analytes S is obtained, since chemical and/or physicalprocesses will be able to change the ionized discharge gas G as afunction of time.

Usual diameters of the discharge paths are between 0.05 mm and 2 mm. Thediameter need, however, not be constant over the entire discharge path.The total flow, discharge gas G and analyte S and, optionally, a dopant,into the analysis unit is typically between 0.005 L/min and 5 L/min. Theratio of discharge gas G to analyte S is typically between 0.1:1-100:1.

The diameter of the sample inlet E is typically between 0.2 mm and 3 mm.In general, a dwell time until the analyzer or the vacuum inlet (at anatmospheric pressure of approx. 80 kPa) is reached will be less than 20ms, if a kinetically controlled ionization is aimed at. For athermodynamically (kinetically) controlled ionization, the dwell timemay be up to 10 s. The dwell time is the time spent by an analyte or aplurality of analytes between the discharge area or the first (in theflow direction, e.g. with ionized discharge gas) coming into contactwith a reactive species and the analysis or introduction into a vacuum.The time depends on the geometric design of an ionization apparatus andits arrangement relative to an analysis unit or a vacuum chamber as wellas on the volume flows of discharge gas G, analyte or analytes S and,optionally, a dopant.

Various features of the embodiments of the disclosed ionizationapparatuses may be combined with other embodiments. In particular, eachionization apparatus may be provided with a charge carrier filter of thetype disclosed here, the first and the second electrode may be arrangedon the outer surface of the dielectric element in each ionizationapparatus, the first and/or the second electrode may be not fullycircumferential or circumferentially interrupted in each ionizationapparatus, the first and/or the second electrode may be sectionwisespiral in shape or helical in shape in each ionization apparatus, thefirst and/or the second electrode may be arranged such that they aredisplaceable relative to each other in each ionization apparatus, thefirst and/or the second electrode may curve outwards in each ionizationapparatus and/or the first and/or the second electrode and/or thedielectric element may curve outwards in each ionization apparatus.

An analyzer can be formed with each ionization apparatus by connecting,optionally directly, the respective ionization apparatus with ananalysis unit. Each analyzer may exhibit a distance of less than 50 mmbetween the first electrode and the outlet of the ionization apparatusand/or may be configured such that and connected to an analysis unitsuch that an analyte or a plurality of analytes will be able to flow, inless than 1 s, over a distance between a discharge area or a firstcoming into contact of a reactive species with an analyte or a pluralityof analytes and an analysis unit or a vacuum chamber.

The respective ionization may be effected as flow-through ionization.

1-94. (canceled)
 95. An ionization apparatus for ionizing an analyte,comprising: an inlet; an outlet; a first electrode; a second electrode;and a dielectric element; wherein the first electrode, the secondelectrode, and the dielectric element are arranged relative to oneanother such that, by applying an electric voltage between the firstelectrode and the second electrode, a dielectric barrier discharge isestablishable in a discharge area in the ionization apparatus; andwherein the first and second electrodes are arranged such that they aredisplaceable or movable relative to each other.
 96. The ionizationapparatus according to claim 95, wherein the first or second electrodeis spiral or helical in shape sectionwise.
 97. The ionization apparatusaccording to claim 95, wherein the second electrode is arranged in thedielectric element sectionwise.
 98. The ionization apparatus accordingto claim 95, wherein the first and second electrodes are displaceablerelative to each other in a flow direction of the analyte through theionization apparatus or in a direction opposite to the flow direction.99. The ionization apparatus according to claim 95, wherein the firstelectrode or the second electrode comprises at least one winding. 100.The ionization apparatus according to claim 95, wherein the smallestdistance between the first electrode and the second electrode during anionization is less than 20 mm.
 101. The ionization apparatus accordingto claim 95, wherein the first electrode is arranged to be displaceablerelative to the dielectric element.
 102. The ionization apparatusaccording to claim 95, wherein the second electrode is arranged to benon-displaceable relative to the dielectric element.
 103. The ionizationapparatus according to claim 95, wherein the pressure in the ionizationapparatus is higher than 40 kPa.
 104. The ionization apparatus accordingto claim 95, wherein the first electrode is arranged outside thedielectric element.
 105. A method of operating an ionization apparatuscomprising an inlet, an outlet, a first electrode, a second electrode,and a dielectric element, wherein: the first electrode, the secondelectrode, and the dielectric element are arranged relative to oneanother such that, by applying an electric voltage between the firstelectrode and the second electrode, a dielectric barrier discharge isestablishable in a discharge area in the ionization apparatus; and thefirst and second electrodes are arranged such that they are displaceableor movable relative to each other; wherein the method comprises:introducing an analyte into the ionization apparatus; ionizing theanalyte in the ionization apparatus by means of a dielectric barrierdischarge in the discharge area; and discharging the ionized analytefrom the ionization apparatus via the outlet.
 106. The method accordingto claim 105, wherein the pressure in the ionization apparatus is higherthan 40 kPa.
 107. The method according to claim 105, wherein a voltageof not more than 20 kV applied between the first electrode and thesecond electrode, so as to generate a dielectric barrier discharge. 108.The method according to claim 105, wherein the dielectric barrierdischarge is caused by unipolar high-voltage pulses with a pulseduration of not more than 1 μs.
 109. The method according to claim 108,wherein the high-voltage pulses have a frequency of not more than 100GHz.
 110. The method according to claim 105, wherein the first andsecond electrodes are supplied with a sinusoidal voltage.
 111. TheMethod according to claim 110, wherein the sinusoidal voltage of oneelectrode being shifted by half a period duration with respect to theother electrode.